I don't see how they could have memory either. Atoms are basically made up of protons, neutrons and electrons, and as far as I know there is no way to distinguish between one electron and another, or one proton and another, etc. True, electrons can change energy states, going from a stable condition to an unstable one, but under normal conditions they tend to quickly revert back to the stable state. Not sure if that could be considered memory, though. But then, I'm not sure they know how human memory works yet.